1. Field of the Invention
The present invention relates to the field of motor vehicle computers; more particularly, it concerns a method of reprogramming a motor vehicle computer, a data storage medium in which reprogramming software is stored, and a motor vehicle computer including a data storage medium of this type.
2. Description of the Related Art
In a known way, a motor vehicle computer takes the form of a microcontroller including, in addition to one or more microprocessors, electronic memories (flash, EEPROM, RAM, etc.), interface peripherals, etc.
Computer program products, or “software”, composed of a set of instructions in program code to be executed by a microprocessor in order to carry out the various tasks of said computer, are stored in non-volatile memories of the computer. As a general rule, three main types of software are stored in non-volatile memories of the computer, as follows:                software known in the English-language literature as “boot software”, to be executed, notably, on the start-up of the computer for the initialization of the latter,        software known in the literature as “application software”, to be executed in order to carry out the specific tasks of the computer,        reprogramming software, also known in the English-language literature as “loader software”, for loading new software intended to replace some or all of the software stored in rewritable non-volatile memories of the computer.        
The boot software and reprogramming software may also be combined in the same piece of software, known in this case as a “boot loader”.
At the present time, boot software, reprogramming software and application software are generally stored in the same rewritable non-volatile electronic memory, for example a flash memory.
Clearly, if the reprogramming software is executed by a microprocessor directly from said flash memory in order to modify the application software and/or the boot software, this will impose constraints for the flash memory, in that said processor will require simultaneous read and write access to the content of said flash memory.
However, current flash memories have limited capacity for simultaneous read and write access. There are known flash memories organized in a limited number of different segments, in which it is possible to have read access to one segment while having write access to another segment. However, it is not uncommon for simultaneous access to be required to the same segment of a flash memory for both writing and reading.
In order to overcome the limited simultaneous read and write access capacity of current flash memories, there is a known way of copying the reprogramming software, before its execution, from the flash memory to a volatile electronic memory such as a RAM memory.
The reprogramming software is then executed from the RAM memory, in such a way that the microprocessor has read access to the content of the RAM memory and write access to the content of the flash memory. This makes it unnecessary to have simultaneous write and read access to the content of the flash memory.
However, it is difficult to implement this approach in motor vehicle computers, since only a limited amount of RAM memory is generally provided, in order to keep the cost of the computer as low as possible.